alt Hacker NewsThere are many DCF77 receivers in Germany that are contained in a square box that's barely large enough for a AA battery; the rest of the square contains the motor/gears and the electronics/receiver (incl. a ferrite loopstick antenna).
The wavelength is around 3.8km...
Yeah, that's because it's receiving an extremely narrowband signal accumulated over a long window so it can suffer the trash efficiency I'm talking about.